A semiconductor device such as an LED or a power-module has a structure in which a semiconductor element is bonded onto a circuit layer made of a conductive material.
In a power semiconductor element for high-power control used to control wind power generation, a transportation system such as an electric automobile and the like, a large amount of heat is generated, and thus, as a substrate mounting the power semiconductor element thereon, for example, a power-module substrate in which a metal sheet having excellent conductive properties is bonded to one surface of a ceramic substrate made of aluminum nitride (AlN) as a circuit layer is widely employed. In addition, in some cases, a metal sheet is bonded to the other surface of the ceramic substrate as a metal layer.
For example, a power-module substrate described in Patent Document 1 has a structure in which copper sheets (copper members) are bonded to both surfaces of a ceramic substrate (ceramic member). In this power-module substrate, the copper sheets are bonded to both surfaces of the ceramic substrate by disposing the copper sheets on the surfaces through Ag—Cu—Ti-based brazing filler metal and carrying out a heating treatment.
Since the above-described Ag—Cu—Ti-based brazing filler metal contains Ti, which is an active metal, when the ceramic substrate and the copper sheets are bonded together through the Ag—Cu—Ti-based brazing filler metal, the wettability between the liquid-phase brazing filler metal and the ceramic substrate becomes favorable, and the ceramic substrate and the copper sheets can be suitably bonded together.